Method for developing land

ABSTRACT

A method for developing a piece of land that is in danger of disappearing due to its small size above a seawater level, including covering the piece of land with a sealing dome larger than the piece of land such that a space is created between the piece of land and the sealing dome and such that a lower edge of the sealing dome is in the sea, securing the sealing dome, while leaving a gap between the lower edge of the sealing dome and a sea bottom, reducing the air pressure inside the sealing dome such that the seawater level inside the sealing dome rises above at least a part of the piece of land to allow coral to naturally grow on the at least the part of the piece of land, and returning the air pressure inside the sealing dome to the same air pressure as outside so that the naturally grown coral on the part of the piece of land becomes calcified coral by being exposure to air, and the calcified coral remains as a developed portion of the piece of land.

TECHNICAL FIELD

The present invention relates to a method for developing land such as an island.

BACKGROUND ART

In small islands such as the Okinotori Islands, for example, coastlines are disappearing due to coastal erosion and rising sea level caused by global warming, and these islands are at risk of going underwater.

According to the IPCC Fourth Assessment Report Working Group I Chapter 5, the global average sea level is estimated to have risen 3.1±0.7 mm/year from 1993 to 2003, and it is reported that by the mid-2090s the global average sea level will have risen 0.22-0.44 m compared to 1990 levels, which is an annual rise of approximately 4 mm, for example.

To deal with this, measures for solving the problem of coastal erosion have been taken, which include placing a plurality of concrete blocks on the sea bottom near the coast so as to absorb the force of approaching waves.

In Patent Document 1, for example, a method of building a natural rock block that is formed by mounting natural rocks on the surface of a concrete block is disclosed. By placing these natural rock blocks on the ground, the current velocity and wave force can be stabilized while maintaining the natural ecosystem, without sacrificing the natural landscape.

As a solution to the problem of disappearing coastline, a method of placing concrete blocks on the sea bottom and growing coral thereon has been implemented. In Patent Document 2, for example, a method for naturally developing coastline is disclosed. In this method, blocks for growing coral that have implantation surfaces on which coral is to be implanted are prepared, live coral is implanted on the implantation surfaces by an adhesive agent, and those blocks are stacked on the sea bottom near the coast to allow the coral to grow thereon, thereby naturally expand the coastline.

RELATED ART DOCUMENTS Patent Documents

-   Patent Document 1: Japanese Patent Application Laid-Open Publication     No. H7-331636 -   Patent Document 2: Japanese Patent Application Laid-Open Publication     No. 2008-017789

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, the above-mentioned methods for building natural rock blocks and growing coral had the following problem.

The function of the natural rock block is nothing more than that of a general concrete block that breaks approaching waves. Also, because coral can only grow in the water, with the conventional coral growing method, which is designed to be implemented underwater, it is not possible to allow coral to grow above water. Therefore, those methods cannot effectively address problems such as rising sea level due to global warming, which is another factor for the vanishing coastline, and thus cannot provide a fundamental solution to the disappearing islands.

Under the United Nations Convention on the Law of the Sea (signed in 1982, came into force in 1996; the Law of the Sea treaty), an island is defined as “a naturally formed area of land, surrounded by water, which is above water at high tide.” Therefore, with the method for building the natural rock block and the method for growing coral described above, it is not possible to develop an island.

The present invention was made in view of the above-mentioned problems, and aims at providing a method for developing land through the workings of nature.

Means for Solving the Problems

In order to achieve the above-mentioned object, a method for developing a piece of land that is in danger of disappearing due to its small size above a seawater level according to the present invention, in one aspect, includes: covering the piece of land with a sealing dome larger than the piece of land such that a space is created between the piece of land and the sealing dome and such that a lower edge of the sealing dome is in the sea; securing the sealing dome, while leaving a gap between the lower edge of the sealing dome and a sea bottom; reducing the air pressure inside the sealing dome such that the seawater level inside the sealing dome rises above at least a part of the piece of land to allow coral to naturally grow on the at least the part of the piece of land; and returning the air pressure inside the sealing dome to the same air pressure as outside so that the naturally grown coral on the part of the piece of land becomes calcified coral by being exposed to air, and the calcified coral remains as a developed portion of the piece of land. Here, “securing” means not only firmly fastening an object by using a bolt and the like, but also moveably fastening an object by a wire or a spring.

In the method for developing land according to the present invention, it is preferable that the sealing dome have an arc-shaped cross section.

In another aspect, a method for expanding a piece of land according to the present invention includes: covering an entire piece of land with a sealing dome such that an air pressure inside can be controlled and such that seawater can flow into and out of the sealing dome; reducing the air pressure inside the sealing dome such that a seawater level inside the sealing dome rises above at least a part of the piece of land to allow coral to naturally grow on the piece of land; and returning the air pressure inside the sealing dome to the same air pressure as outside after the coral has grown to an arbitrary target size so that the naturally grown coral on the piece of land becomes calcified coral by being exposed to air, the calcified coral remaining as an expanded portion of the piece of land.

Effects of the Invention

According to the first aspect of the present invention, by reducing the air pressure inside the sealing dome, the water level in the sealing dome can be raised above the island, allowing the coral to naturally grow on the island. This makes it possible to develop land through the workings of nature.

When the sealing dome has an arc-shaped cross section, the sealing dome can be provided with a sufficient strength to withstand the atmosphere pressure acting thereon when the air pressure is reduced.

Further, according to the second aspect of the present invention, by increasing the air pressure inside the sealing dome so as to lower the water level in the sealing dome, the underwater rock is exposed above sea-level, increasing an area of land. This makes it possible to develop land through the workings of nature.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1D are schematic cross-sectional views showing a method for developing land according to an embodiment of the present invention.

FIGS. 2A and 2B are schematic cross-sectional views showing a method for developing land according to a second embodiment of the present invention.

FIGS. 3A and 3B are a more detailed plan view and cross-sectional view showing an embodiment of a method for developing land according to the present invention.

FIGS. 4A and 4B are a plan view and cross-sectional view in which a center part has been magnified.

FIG. 5 is a view in which the pump has been magnified.

FIGS. 6A to 6F are views showing a method of making the sealing dome.

FIGS. 7A to 7C are cross-sectional views as seen from a side view, plan view, and front view, showing a seismically isolated rubber structure.

DETAILED DESCRIPTION OF EMBODIMENTS

First, terms that are used in the present specification will be defined. A coral reef is a geological formation created by clusters of reef-building coral, the coral itself being a tiny organism called a polyp. Polyps attach to the sea floor and split up, and once grown are called coral. Over time, a coral will grow and attach to other corals, forming a coral reef. Coral skeletons are made of a calcareous substance (calcium carbonate). The mineral of coral skeletons is aragonite, which has a specific gravity of approximately 2.9, a Mohs hardness of approximately 4, and a compressive strength of approximately 12.4 Mpa (126.48 kgf/cm²). (See NISHIKAWA, Tetsunari, Characteristics and new bone formation of coral as an ideal sacaffold, Research Project Number: 19592273, https://kaken.nii.ac.jp/pdf/2010/seika/jsps/34408/19592273 seika.pdf)

Under the United Nations Convention on the Law of the Sea Article 121(1), an “island” is defined as “a naturally formed area of land, surrounded by water, which is above water at high tide.” In other words, an “island” as recognized by the United Nations is that which satisfies the above requirements, and is unrelated to the area, altitude, and formative materials thereof.

Jeep Island, which is located in Chuuk (formerly Truk) Lagoon in the Federated States of Micronesia, is said to be the smallest inhabited island in the world, and has a diameter of approximately 34 m and an outer circumference of approximately 110 m, which is an area of approximately 1000 m². Incidentally, the Tokyo Dome has a ground area of approximately 13,000 m².

Furthermore, among the Okinotori Islands of Japan, which are internationally recognized as “islands” and designated as an exclusive economic zone, the portion of Kita-Kojima in the reef has an area of 7.86 m² and a height of 16 cm at high tide, and Higashi-Kojima has an area of only 1.58 m² and a height of 6 cm. As described above, the global sea level is rising year by year, and this rise is thought to be accelerated by the effects of global warming and the like. If the above-mentioned estimates are correct, and the sea level rises 0.22-0.44 m compared to 1990 levels by the mid-2090s, then the Okinotori Islands could go underwater.

Islands that are at risk of going underwater, such as these Okinotori Islands, are an example of exactly the kind of island that the method for developing land of the present invention is targeting. Namely, by applying the method for developing land of the present invention to islands or the like with a heightened risk of going underwater in the future due to sea level rises, such risk can be prevented. As described later, it is also possible to develop land for other reasons for other islands of a size equivalent to those islands that will go underwater.

As also described later, in the process of developing the land, a reef that has grown underwater will immediately perish if constantly exposed to outside air after the dome is removed, but the calcified part of the coral, which is the skeleton, will remain.

Below, embodiments of the present invention will be explained in detail with reference to figures.

FIGS. 1A and 1B are schematic cross-sectional views showing a method for developing land according to an embodiment of the present invention. As shown in FIG. 1A, an island 1 has an aboveground portion 1 a exposed above the sea level 2.

In the method for developing land of the present embodiment, in this state, the island 1 is covered with a sealing dome 3 larger than the aboveground portion 1 a such that a space s1 is created between the island 1 and the sealing dome 3 and such that a lower edge 3 a of the sealing dome 3 is located in the sea, i.e., below the sea level 2 as shown in FIG. 1B. Because of the arc-shaped cross section, the sealing dome 3 has a sufficient strength to withstand the atmosphere pressure acting thereon when the air pressure is reduced. It is preferable that the sealing dome 3 be made of a transparent material that is light and strong such as polycarbonate, but other materials may also be used.

Next, leaving a gap s2 between the lower edge 3 a of the sealing dome 3 and a sea bottom 1 b, piles 4 secured to the lower edge 3 a of the sealing dome 3 with bolts (not shown) are driven into the sea bottom 1 b to secure the sealing dome 3. The piles 4 can be made of stainless or the like. Because the figure shows a cross-sectional view, only two piles on the right and on the left are shown, but in the actual sealing dome 3, the piles are provided at even intervals along the lower edge 3 a.

Next, a pump 5 provided in the sealing dome 3 is actuated to reduce the air pressure inside the sealing dome 3. According to the Pascal's law, as indicated by the arrows in FIG. 1B, this causes the seawater to be drawn into the sealing dome 3, allowing the sea level 2 a inside the sealing dome 3 to rise above the aboveground portion 1 a of the island 1.

By leaving the island 1 under this condition, coral 6 will naturally grow on the island 1.

After coral 6 has grown, as shown in FIG. 1C, the pump 5 is released to make the air pressure inside the sealing dome 3 equal to the atmosphere pressure outside of the sealing dome 3. This causes the sea level 2 a inside the sealing dome 3 to lower to the same level as the sea level 2 outside of the sealing dome 3.

Even when the sealing dome 3 is thereafter removed, because the coral skeletons form land, the elevation of the highest point of the island 1 becomes higher than that in the original state. As a result, as shown in FIG. 1D, even if the sea level 2 rises from the original sea level 2 a due to global warming and the like, and the original aboveground portion 1 a is submerged, it would not cause the entire island to be submerged because the elevation of the highest point of the island has been raised by the height of the coral 6. In this way, land can be developed through the workings of nature. Also, by repeating the above-mentioned steps, even if the sea level further rises, the island can be saved from going underwater.

FIGS. 2A and 2B are schematic diagrams showing a method for developing land according to a second embodiment of the present invention. As shown in FIG. 2A, a top portion 11 a of an underwater rock 11 is not exposed above the sea level 2.

In the method for developing land of the present embodiment, in this state, as shown in FIG. 2B, the underwater rock 11 is covered with a sealing dome 13 larger than the top portion 11 a thereof that becomes an aboveground portion of the island such that a space s11 is created between the underwater rock 11 and the sealing dome 13 and such that a lower edge 13 a of the sealing dome 13 is located in the sea, i.e., below the sea level 2. Because of the arc-shaped cross section, the sealing dome 13 is provided with a sufficient strength to withstand the atmosphere pressure acting thereon when the air pressure is increased. It is preferable that the sealing dome 13 be made of a transparent material that is light and strong such as polycarbonate, but other materials may also be used.

Next, leaving a gap s12 between the lower edge 13 a of the sealing dome 13 and a sea bottom 11 b, piles 14 that are secured to the lower edge 13 a of the sealing dome 13 with bolts (not shown) are driven into the sea bottom 11 b to secure the sealing dome 13.

Thereafter, by actuating a pump 15 provided in the sealing dome 13, the air pressure inside the sealing dome 13 is increased. According to the Pascal's Law, this causes the sea level inside the sealing dome 13 to lower to a level below the top portion 11 a of the underwater rock 11 as indicated by the arrows in FIG. 2B.

FIGS. 3A to 5 show the embodiments of a method for developing land of the present invention in more detail. FIG. 3A is a plan view showing an embodiment of a method for developing land according to the present invention, FIG. 3B is a cross-sectional view thereof, FIG. 4A is a plan view in which a center part has been magnified, FIG. 4B is a cross-sectional view thereof, and FIG. 5 is a view in which the pump has been magnified. FIGS. 6A to 6F are views showing a method of making the sealing dome, and FIGS. 7A to 7C are cross-sectional views as seen from a side view, plan view, and front view, showing a seismically isolated rubber structure. In this embodiment, an island 21 can be a reef island approximately the size of Kita-Kojima (an area of 7.86 square meters and a height of 16 centimeters) or Higashi-Kojima (an area of 1.58 square meters and a height of 6 centimeters) in the Okinotori Islands, for example.

By applying the present embodiment to islands that are “at risk of going underwater” as described above, the land area will be increased by exposing the underwater rock from sea level, and land will be developed by the workings of nature, thereby making it possible to reduce the danger of the island going underwater.

Examples of islands for which such effects can be attained include those with a maximum radius of less than or equal to 3 m and preferably less than or equal to 1 m (above water at high tide) or a height from the ocean surface of less than or equal to 3 m and preferably less than or equal to 1 m (above water at high tide).

Islands of such size are at a high risk of disappearing due to rising sea levels rising and wave erosion caused by global warming.

Even for islands that are not at risk of going underwater or the like (including exposed rocks, reef flats, reef ridges and the like that are underwater at high tide but above water at low tide), it goes without saying that the method for developing land of the present invention can be applied to islands of an equivalent size where land development is necessary for whatever reason.

This method for developing land by coral reefs can be applied wherever it is possible to grow coral reef, even if such a location is not the ocean. That is to say, as long as there is seawater and sun, this method can also be applied to salt lakes and the like, for example. Furthermore, the method can be applied to facilities such as aquariums, to simulations before actual implementation at sea, to forming natural embankments, and the like.

The part of the island 21 at an aboveground part is exposed more at the top than a maximum high tide surface 22 a and minimum low tide surface 22 b. As shown in FIG. 4B, in the method for developing land of the present embodiment, the island 21 is covered by a sealing dome 23 that is larger than the aboveground part 21 a of the island in a state in which a gap s21 is present between the island 21 and the sealing dome 23 and in which a lower edge 23 a of the sealing dome 23 is in the water, or in other words, is located lower than the minimum low tide surface 22 b.

The sealing dome 23 has a diameter approximately 1 to 3 m greater than the outer diameter of land above the ocean surface (at high tide) of the island, for example. If the diameter of the sealing dome 23 is less than 1 m greater than the outer diameter of the land, there will be adverse effects on the growth of the coral due to deterioration of water quality, a rise in water temperature, lack of oxygen, and the amount ultraviolet light. If the diameter of the sealing dome is more than 3 m greater than the outer diameter of the land, construction will be difficult and not economical depending on the installation environment.

The cross-section of the sealing dome 23 is an arc-shape; thus, the sealing dome 23 can maintain enough strength to withstand atmospheric pressure acting thereon when the air pressure is reduced. The sealing dome 23 is constituted of transparent acrylic resin layers, and has a thickness of 65 millimeters. In a plan view the sealing dome 23 has a round shape with a diameter of 5 meters. In the drawings the size of each part is shown in millimeter units.

The lower edge 23 a of the sealing dome 23 is fastened to a seismically isolated rubber structure 23 b by a stainless bolt 23 c (see FIG. 7C), and as shown in FIGS. 4B and 7 this seismically isolated rubber structure 23 b is fastened to an inner peripheral bottom 71 of a concrete protective barrier 7 constructed on a sea floor 21 b by using stainless piles 23 d. This seismically isolated rubber structure is for alleviating the effects on the sealing dome 23 during an earthquake. In areas where earthquakes are rare, a hard material may be used.

As shown in FIGS. 7A to 7C, the seismically isolated rubber structure 23 b includes: a sole plate 23 e connected to the lower edge 23 a of the sealing dome 23; a tray-shaped base pot 23 i fastened to the inner peripheral bottom 71 of the concrete protective barrier 7; a slide plate 23 f interposed between these; a piston 23 g and an elastomer 23 h as a cushioning member located inside the base pot 23 i.

As shown in FIG. 4A, the seismically isolated rubber structure 23 b is installed at eight locations at equal distances to each other in a plan view, to form a circle along the lower edge 23 a of the sealing dome 23. There are gaps s22 between the lower edge 23 a of the sealing dome 23 and the ocean floor 21 b in areas at the lower side of the lower edge 23 a of the sealing dome 23 where there is no seismically isolated rubber structure 23 b, and thus, seawater can flow freely into and out of the sealing dome 23.

The donut-shaped concrete protective barrier 7, which is made of a water and salt-resistant concrete that does not dissolve in water, is constructed around the sealing dome 23. This concrete protective barrier 7 is constructed on the ocean floor 21 b such that the inner peripheral bottom 71 is positioned on the lower edge 23 a of the sealing dome 23 and the lower side of the seismically isolated rubber structure 23 b and encircles the reef island 21. A barrier-like part 72 is established around this inner peripheral bottom 71. A top surface 72 a of the barrier-like part 72 is higher than the top of the sealing dome 23, and an inner wall 72 b of the barrier-like part 72 is an octagonal shape in a plan view and provided vertically. The inner wall 72 b encircles the sealing dome 23 at a location that is approximately one meter from the outside of the sealing dome 23. The top surface 72 a of the concrete protective barrier 7 is a horizontal portion with a width of approximately 1.5 meters disposed on the outside of this inner wall 72 b, and a net 72 c for blocking falling objects is hung on the inner edge of the top surface 72 a so as to cover the top of the sealing dome 23.

A pump unit 25, described later, is installed on the top surface 72 a of the concrete protective barrier 7. An outer periphery 72 d of the concrete protective barrier 7 has a slope-shape with a 30 degree angle so as to become lower in height the further out the outer periphery 72 d is. This cushions the effects of waves. Solar panels 28 are installed on the top of the outer periphery 72 d at a location higher than the maximum high tide surface 22 a. These solar panels 28 are power units that are water and salt-resistant, and provide power to the pump unit 25. A donut-shaped loop part 72 e having a top surface that is horizontal is disposed on the exterior of the outer periphery 72 d. The top surface of the loop-shaped part 72 e is lower than the maximum high tide surface 22 a and higher than the minimum low tide surface 22 b.

The concrete protective barrier 7 has seawater entrance routes 72 f and 72 g in the horizontal and vertical direction in a plan view. Specifically, the seawater entrance route 72 f disposed in the horizontal direction in the plan view shown in FIG. 4A goes from the outer periphery of the concrete protective barrier 7 to the inner periphery in a trench-shape that reaches the bottom of the concrete protective barrier 7, or namely, the ocean floor. The bottom of the seawater entrance route 72 f is lower than the minimum low tide surface 22 b; therefore, seawater flows into the concrete protective barrier 7 and then flows into the sealing dome 23 through this seawater entrance route 72 f. The seawater can also flow to the outside of the concrete protective barrier 7 from the sealing dome 23, and thus, in a state where air pressure inside the sealing dome 23 has not been adjusted, the ocean surface inside the sealing dome 23 would be the same height as an ocean surface 22 outside the concrete protective barrier 7.

In the plan view shown in FIG. 4A, the seawater entrance route 72 g disposed in the vertical direction goes from the outer periphery 72 d of the concrete protective barrier 7 to the inner wall 72 b in a trench-shape that reaches from the top surface 72 a to the top surface of the loop-shaped part 72 e. The bottom of the seawater entrance route 72 g is lower than the maximum high tide surface 22 a; therefore, seawater flows into the concrete protective barrier 7 and then flows into the sealing dome 23 through this seawater entrance route 72 g at high tide.

The concrete protective barrier 7 is surrounded by wave-dissipating blocks 7 h, and this prevents the concrete protective barrier 7 from being eroded by waves. In the plan view shown in FIG. 4A, only the top side of the concrete protective barrier 7 does not have the wave-dissipating blocks 7 h. In this location, the loop-shaped part 72 e protrudes outward in a circumferential direction to provide a dock 7 i. If a boat lands at the dock 7 i, the loop-shaped part 72 e, outer periphery 72 d, and top surface 72 a can be walked on to access the solar panels 28, pump unit 25, and sealing dome 23. There are cases in which installing the protective barrier 7 causes damage to some of the coral, but installation is possible without damaging the coral present under the ocean surface surrounding the island 21 by installing the protective barrier 7 and sealing dome 23 in a donut-shape slightly separated from the island 21.

The pump unit 25 is housed in a tower (not shown) installed on the top surface 72 a of the protective barrier 7. The pump unit 25 has one end connected in an airtight configuration to the top of the sealing dome 23, and as shown in FIG. 5, includes: an intake pipe 25 a that is 50 millimeters in diameter and that goes inside the sealing dome 23; an intake motor valve 25 b disposed on the other end of this intake pipe 25 a; an air-supply pipe 25 c that is 25 millimeters in diameter and that has one end connected to a portion of the intake pipe 25 a that is closer to the sealing dome 23 than the intake motor valve 25 b; a vacuum unit 25 d that has one side connected to the other end of this air-supply pipe 25 c; an exhaust 25 g that is disposed on the other side of this vacuum unit 25 d; a check valve 25 e disposed at a midpoint of the air-supply pipe 25 c; a motor valve 25 f that is disposed closer to the intake pipe 25 a than this check valve 25 e on the air-supply pipe 25 c; a suction pipe for cooling water 25 h that is disposed forking closer to the pump 25 d than this check valve 25 e on the air-supply pipe 25 c and that has one end open in the ocean outside the sealing dome 23; a motor valve 25 i disposed at a midpoint of this suction pipe for cooling water 25 h; and a control panel 25 j that controls the respective motor valves 25 f, 25 i, and 25 b and the vacuum unit 25 d. The intake motor valve 25 b is closed when the vacuum unit 25 d is in operation to raise the ocean surface inside the sealing dome 23 and when this state is being maintained, and open when air intake is performed in the sealing dome 23 in order to lower the ocean surface inside the sealing dome 23.

The suction pipe for cooling water 25 h is a pipe for injecting seawater to the vacuum unit 25 d to cool the area around the vacuum unit 25 d. When this cooling is being performed, the motor valve 25 i is open, and the motor valve 25 f is closed. This cooling can be performed at five minute intervals, for example.

When operating the pump unit 25, air inside the sealing dome 23 flows into the vacuum unit 25 d through the air-supply pipe 25 c and is discharged from the exhaust 25 g. At this time, the intake motor valve 25 b is closed, and the check valve 25 e prevents air from moving from the pump 25 d towards the intake pipe 25 a. Thus, the drop in air pressure inside the sealing dome 23 causes seawater to flow into the sealing dome 23 from the gaps s22 between the lower edge 23 a of the sealing dome 23 and the ocean floor 21 b. Continued operation of the pump unit 25 raises the ocean surface 22 a inside the sealing dome 23 to the top of the aboveground part 21 a of the island 21.

Left in the above state, coral 26 will naturally grow on the island 21.

After the coral 26 has grown, opening the intake motor valve 25 b causes air to flow from the intake motor valve 25 b into the sealing dome 23 through the intake pipe 25 a, and the air pressure inside the sealing dome 23 will become equal to the air pressure outside the sealing dome 23. Following this, the ocean surface inside the sealing dome 23 falls until it is the same height as the ocean surface outside the sealing dome 23.

In the above state, even if the sealing dome 23 is removed the calcified coral develops land, and the height above sea level of the top of the island 21 will be higher than it was initially. Thereafter, even if global warming or the like raises the ocean surface above the initial ocean surface 22 a, the height above sea level of the top of the island will be taller in accordance with the coral 26 as described above; thus, even if the aboveground part 21 a is submerged, the island 21 itself will not be submerged.

An acrylic dome, which is used for the sealing dome 23 described above, is formed by shape allocations as shown in FIGS. 6A to 6F. In other words, the acrylic dome is made of the three separate panels shown as A, B, and C. These panels are assembled together by a polymerization adhesive. The plate thickness of the acrylic dome is configured at 65 mm with a design pressure calculated at 0.5 kgf/cm². The world's largest cylindrical tank, in the Morocco Mall, has a diameter of 12.1 meters, a height of 7.8 meters, and a thickness of 12 centimeters.

A method of manufacturing the acrylic dome is explained in detail below. First, acrylic base plates with a thickness of 30 mm are made. Next, as shown in FIG. 6C, two of the acrylic base plates are bonded together. The two acrylic base plates, each with a thickness of 30 mm, are layered together with a polymerization adhesive having a thickness of 5 mm, thus forming a laminate plate with a thickness of 65 mm. This laminate plate with a thickness of 65 mm is heated in a furnace and molded using a prescribed molding tool to form the panels A, B, and C, shown in FIGS. 6D, 6E, and 6F, respectively. These panels are cut with precision into sizes that can be bonded. A bonding jig is used for the polymerization bonding of the divided panels A and B, thereby forming a panel of six plates in which A and B are bonded. The combined panels of the steps described above are transported to a temporary plant (such as a warehouse) near a harbor and then a bonding jig is used for polymerization bonding to assemble the panels into a state shown in FIGS. 6A and 6B.

An example of technological features the vacuum unit used to implement the present invention should have is given below. The vacuum unit can have excellent water, salt, and corrosion resistance and durability by using a resin for the vacuum generating part and also having the injector driver pump, tubes, and the like be made of a resin. Moreover, even if water gets mixed in from the intake side, there would be no overload on the pumps and no drop in the vacuum level. Furthermore, ocean water can be used as supplementary water, and operation is possible even if external water sources such as water utilities cannot be reached.

Gas that can be handled includes air at 0-40° C., for example, the maximum suction amount of air cab be 901/min at a driving water temperature of 25° C., for example, the negative pressure resistance can be 15 kPA or the like, for example, and the installation place can be indoors (when housed in a tower) or outdoors. Alternating current output can be single-phase, for example, the rated voltage (V) can be 100, for example, and the rated frequency (Hz) can be 50/60 or the like, for example. An example of a pump that satisfies the above is the Ebara PQM plastic self-priming pump (Ebara Corporation 40PQM5.4S 0.4 kw single-phase 100V 60 Hz, using three).

An example of technological features that a solar power generating unit used to secure power for the above-mentioned vacuum unit made of a resin should have is given below.

Installation Capacity (kW)  24 Installation Place Indoors or Outdoors Ambient Temperature (° C.)  0 to 40 Ambient Humidity (%) 10 to 90 Alternating Current Output Single-phase Rated Voltage (V) 100 Rated Frequency (Hz) 50/60

The solar power generating unit can have the water and salt resistance thereof increased by being coated with a plastic film and covered with a case.

As an example of a solar power generating unit that satisfies the above conditions, the following can be combined to obtain a desired solar power generating unit: 20 independent type KD135SK-RP solar panels that have protection against salt damage, made by Kyocera Corporation; two TS-60 charge/discharge controllers, made by Morningstar, Inc.; 20 PVX-2580L deep cycle batteries, made by Concorde Battery Corporation; and three SK3000 DC-AC Pure Sine Wave Inverters, made by COTEK.

As a seismically isolated rubber structure, the pillar uniton support made by Nippon Pillar Packing Co., Ltd. shown in FIGS. 7A to 7C can be used, for example.

The growth rate for coral is as follows:

Dendritic Coral Approximately 10-20 cm/year

Massive Coral Approximately 0.5-1 cm/year

Coral Reef Approximately 40 cm/100 years

The illuminance needed for cultivating coral is as follows:

Optimal 120,000 to 100,000 lx Mostly Sunny Weather Suboptimal 100,000 to 50,000 lx Mostly Clear Weather

A desirable seawater environment in order to grow the coral described above is as follows:

Surface Seawater Temperature: 25 to 29° C.

Seawater Saline Concentration: 3.3 to 3.7%

In order to maintain water quality, it is desirable to implement one or more of the below:

1) Seawater inside the sealing dome 23 being replaced by opening and closing of the intake motor valve 25 b.

2) Suppressing a rise in water temperature by covering the sealing dome 23 with an infrared cut film.

3) Blocking harmful ultraviolet rays by covering the sealing dome 23 with an ultraviolet cut film.

(See notes on light as an essential and lethal environmental factor for coral reef organisms, Kazuhiko Fujita, Iwao Kenji, Midoriishi, No. 13, March 2002, http://www.amsl.or.jp/midoriishi/13_(—)04.pdf)

By exposing the underwater rock from the sea level as described above, an island can be formed, and an area of land can be increased. Thus, it is possible to develop land through the workings of nature.

In the present embodiment, the island will disappear when the sealing dome 13 is removed. However, even if the sea level 12 further rises, by further increasing the air pressure inside the sealing dome 13, the island can be saved from going underwater.

In implementing the present invention, various modifications can be made without departing from the spirit thereof. For example, the method of increasing or decreasing the pressure inside the sealing dome described above is not limited to the method using a pump, but various known methods can be employed such as a chemical reaction, dissolution into sea water, or reduction of volume by cooling a vapor. In securing the sealing dome to the sea bottom, the sealing dome may be moveably fastened by wires or springs, instead of being firmly fastened by bolts or the like. The sealing dome may be secured to an above-water portion of the island, instead of the sea bottom. The sealing dome may have other cross section shapes than the arc shape, and may be provided with thermal insulating films or solar panels on the surface thereof for temperature control and the like.

As described above, the method for developing land according to the present invention, in one aspect, includes: covering an island with a sealing dome larger than an aboveground portion of the island such that a space is created between the island and the sealing dome and such that a lower edge of the sealing dome is located in the sea; securing the sealing dome, while leaving a gap between the lower edge of the sealing dome and the sea bottom; and reducing the air pressure inside the sealing dome such that a water level inside the sealing dome rises above the island to allow coral to naturally grow on the island, thereby developing land. In this method, by reducing the air pressure inside the sealing dome, the water level inside the sealing dome is raised above the island, which allows coral to naturally grow on the island, and therefore, land can be developed through the workings of nature. In the case of increasing the area of land by: covering an underwater rock with a sealing dome larger than a portion of the underwater rock that becomes an aboveground portion such that a space is created between the underwater rock and the sealing dome and such that a lower edge of the sealing dome is located in the sea; securing the sealing dome, while leaving a gap between the lower edge of the sealing dome and the sea bottom; and increasing the air pressure inside the sealing dome such that a water level inside the sealing dome lowers to expose the underwater rock above sea-level, the area of the land can be increased by increasing the air pressure inside the sealing dome such that a water level inside the sealing dome lowers to expose the underwater rock above sea-level. Therefore, it is possible to develop land through the workings of nature.

Descriptions of Reference Characters  1 island  2, 12 sea level  3, 13 sealing dome  4, 14 pile  5, 15 pump 11 underwater rock 

1. A method for developing a piece of land that is in danger of disappearing due to its small size above a seawater level, comprising: covering the piece of land with a sealing dome larger than the piece of land such that a space is created between the piece of land and the sealing dome and such that a lower edge of the sealing dome is in the sea; securing the sealing dome, while leaving a gap between the lower edge of the sealing dome and a sea bottom; reducing the air pressure inside the sealing dome such that the seawater level inside the sealing dome rises above at least a part of the piece of land to allow coral to naturally grow on the at least the part of the piece of land; and returning the air pressure inside the sealing dome to the same air pressure as outside so that the naturally grown coral on the part of the piece of land becomes calcified coral by being exposed to air, and the calcified coral remains as a developed portion of the piece of land.
 2. The method for developing a piece of land according to claim 1, wherein the sealing dome has an arc-shaped cross section.
 3. (canceled)
 4. A method for expanding a piece of land, comprising: covering an entire piece of land with a sealing dome such that an air pressure inside can be controlled and such that seawater can flow into and out of the sealing dome; reducing the air pressure inside the sealing dome such that a seawater level inside the sealing dome rises above at least a part of the piece of land to allow coral to naturally grow on the piece of land; and returning the air pressure inside the sealing dome to the same air pressure as outside after the coral has grown to a target size so that the naturally grown coral on the piece of land becomes calcified coral by being exposed to air, and the calcified coral remains as an expanded portion of the piece of land.
 5. The method for expanding a piece of land according to claim 4, wherein the covering step includes forming a hemispherically-shaped sealing dome by bonding a plurality of arch-shaped members.
 6. The method for expanding a piece of land according to claim 4, wherein the covering step includes forming the sealing dome including a transparent area to allow the piece of land to receive sunlight sufficient to grow coral.
 7. The method for expanding a piece of land according to claim 4 further comprising: forming a protective barrier including an bottom flange placed on a sea floor, the bottom flange being installed below the sealing dome, wherein the covering step includes installing the sealing dome on the bottom flange of the protective barrier, and at least one gap is formed between the sealing dome and the bottom flange so that the seawater flows freely into and out of the sealing dome.
 8. The method for expanding a piece of land according to claim 7, wherein the protective barrier includes a barrier wall installed on the bottom flange, the barrier wall being installed along an outside of the sealing dome.
 9. The method for expanding a piece of land according to claim 7, wherein at least one seismically isolated rubber structure is formed between the sealing dome and the bottom flange of the protective barrier.
 10. The method for expanding a piece of land according to claim 7, wherein the protective barrier is made of a water-resistant and salt-resistant material.
 11. The method for expanding a piece of land according to claim 7, further comprising: forming a plurality of wave-dissipating blocks along an outside of the protective barrier.
 12. The method for expanding a piece of land according to claim 8, wherein a height of the barrier wall is larger than a height of the sealing dome.
 13. The method for expanding a piece of land according to claim 8, wherein an outer periphery of the barrier wall has a slope shape to buffer sea waves.
 14. The method for expanding a piece of land according to claim 4, wherein the sealing dome is formed of a plurality of separate panels made of acrylic resin.
 15. The method for expanding a piece of land according to claim 14, wherein each of the plurality of separate panels is made from a laminate plate laminated by a plurality of acrylic base plates.
 16. The method for expanding a piece of land according to claim 14, wherein the covering step includes forming a hemispherically-shaped sealing dome by using polymerization bonding to assemble the plurality of the separates panels.
 17. The method for expanding a piece of land according to claim 4, further comprising: covering the sealing dome with an ultraviolet cut film to block ultraviolet rays harmful to coral growth.
 18. The method for expanding a piece of land according to claim 4, further comprising; adjusting at least one of a seawater temperature and a seawater saline concentration inside the sealing dome to an appropriate value until the coral grows to the target size. 